mbrsagor / postgresql

How to use postgresql basic command line

Here, basic Database commoand line for all developer. I think it should need to know for every developer.

Postgresql database basic operations

How to install PostgreSQL on a Mac with Homebrew and Lunchy?

$ brew update $ brew doctor

Install Postgres

$ brew install postgresql

Create/Upgrade a database

$ initdb /usr/local/var/postgres -E utf8

Install Lunchy

$ gem install lunchy

Start/Stop Postgres

$ mkdir -p ~/Library/LaunchAgents $ cp /usr/local/Cellar/postgresql/9.2.1/homebrew.mxcl.postgresql.plist ~/Library/LaunchAgents/

Since we're using Lunchy, we don't need to run this third command: $ launchctl load -w ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist

Instead, we'll simply use this to start Postgres: $ lunchy start postgres

To stop Postgres: $ lunchy stop postgres

How to access postgrad shell?

psql postgres

How to create database?

CREATE DATABASE db_name;

List of Database.

\l

How to change database password.

\password

How to drop database ?

DROP DATABASE db_name;

How to switch database?

\c db_name

How to create User?

CREATE USER user_name;

How to drop User?

DROP USER user_name;

List of users.

\du

Many time we need to import or export database. In this tutorial I will show you how to import and export the postgress database.

Import database

Open your terminal then run the command psql -U db_user db_name < ~/Desktop/db/my_db.sql

Export be simular

pg_dump -U sagor -h localhost mydb >> ~/Desktop/mydb.sql Here sagor means my database username.

Install postgresql pip

pip install postgres

How to use postgress database in Django web app?

1. First you active your virtualenv then pip install django psycopg2

2. Then configuration Django setting.py file look like this:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql2',
        'NAME': 'my_db',
        'USER': 'db_user',
        'PASSWORD': '123',
        'HOST': 'localhost',
        'PORT': '5432',
    }
}

create a database user which we will use to connect to and interact with the database.

CREATE USER mbrsagor WITH PASSWORD 'sagor123';

we need to do is give our database user access rights to the database we created:

GRANT ALL PRIVILEGES ON DATABASE my_db TO my_user;

How to create table?

CREATE TABLE student (
id INT NOT NULL PRIMARY KEY,
first_name VARCHAR(50) NOT NULL,
last_name VARCHAR(50) NOT NULL,
gender VARCHAR(10) NOT NULL,
email VARCHAR(75),
date DATE);

Then show table data using \d

List of relations in table.

\d table_name; \dt

How to drop table?

DROP TABLE table_name;

Insert data into table.

INSERT INTO student(first_name, last_name, gender, date, email)
VALUES('mbr', 'sagor', 'yes', date '2020-10-10', '[e-mail]');

How to Query data from the table?

SELECT * FROM table_name;

Select from WHERE.

SELECT FROM table_name WHERE table_field='value';

Start database: pg_ctl -D /opt/homebrew/var/postgres start

Access database: sudo -u postgres psql

DB backup: pg_dump -U sagor -h localhost dev >> dev.sql

DB import: psql -h localhost -U postgres -d postdata -f D:\Backup\database.sql

Download DB from Cloud scp -i sos.pem ubuntu@ip_address:~/dev.sql .